Generally, if this is your primary source of base load power, you'll want it to run constantly. With that in mind:
(1) HP boilers are more efficient than LP boilers. You can look at the bottom of the Nether for Firestone, which can be refined and used to fire a HP boiler up. If it still works like last year, that is.
(2) Big boilers are more efficient than small boilers. I recommend using one big one instead of three small ones.
(3) There is an adjunct multiblock to the steam boiler - the steam oven I think it's called. It can be used to make charcoal, and with a constant supply of wood it's fast enough to supply a maximum-size HP steam boiler with charcoal after the initial heat-up phase. After the initial heat-up it runs on the steam boiler's own steam.
(4) MFR is still the best mod for tree farming if you go for reliablity since it has no moving parts (like Steve's Carts) and it doesn't need maintenance (like EnderIO's farming station). All three methods are efficient, but the Steve's Cart's woodcutter is a PITA to repair and the Galgadorian stuff is insanely expensive. So a Steve's Carts tree farm nullifies one of the main advantages of a tree farm as a power source: that it's avaialble eary with relatively low expense while still working reliably.
(5) If you want to increase growth, an OpenBlocks sprinkler gives you a good effect for the almost negligible effort to make and run it, even if you don't supply it with bonemeal. Works with any tree farm option. MFR fertilizer can result in absolutely insane growth speeds if your farm gets a constant supply, but its large-scale production requires some additional logistics and possibly even a second farm (making wheat).
It's not fair to say that Steve's carts isn't available early on. Iron, gold, redstone and you'll be on your way. Actually I would argue that Steve's Carts tree farm is available earlier than MFR simply because you have to be able to make invar in most of the recipes (ferrous). That being said anything beyond the basic 3x3 requires gems and depending on the pack and recipe can be anything from metals to emeralds. Granted you can make more than 1 harvester and planter but again more raw materials which includes rubber and invar. This also means finding rubber which in some biomes can be very difficult. I'm not saying that Steve's Carts is easy to setup, tracks alone can be a pain. However I am saying that it can be cheaper depending on the size of the farm.
You still have to power the MFR planter and harvester. And you have to have a way to transport items to and from the machines. If you just place a chest behind the harvester it will fill up quickly. If you don't have a way to transport sapplings to the planter you will find yourself hacking through trees manually to get to it from above or construct it with a tunnel to walk the things to it. Now we are looking at various mods to move the stuff.
Enderio - does the job very well but takes an alloy furnace and ender pearls in addition to filters which if you're using the basic takes paper and hoppers
Thermal Dynamics (finally! woot) - which requires lead and then an upgrade for the servo on the pipe. Then you're sorting through different chests just to get the sapplings back to the planter. It takes up more space because the power and items can't occupy the same space (or did they change that?)
Buildcraft pipes - great mod and good at sorting. In fact if I don't have ender pearls I use this for steve's carts. Pumping back to the harvester brings the same issue though of sorting and handling overflow from the planter
AE conduit - granted great setup but honestly not easily setup and very material heavy and not early game at all.
Factorization - LOL (it can do it, the LOL is because F if I know how)
Computercraft - Very easy to craft turtles, hard to program and I don't know of a program that will easily move items that you want to the way you would need to...
I can't think of other methods of moving things off the top of my head.
Now after you do all of that you have to turn it into charcoal which means additional machines. So now you're setting up vanilla furnaces with chests and hoppers (which is also fun but not compact), ender io alloy furnaces, redstone furnaces, ic2 furnaces, etc and make sure you make enough to keep up with the size farm you have.. and you must have enough or large enough farms to keep up with the steam boilers...
All of this is contained in one Steve's Cart.
All of that being said I do use MFR lol for some things
See what happens when I'm bored at work...